Nyx Avatar

"That was my name for a time... I didn't mind it. I am merely a harbinger of the Fall... Although, Nyx and myself are now one in the same."

—Nyx Avatar, Persona 3

Nyx Avatar is the final boss of Persona 3 (The Journey for FES version, as Erebus is the final boss of The Answer).

It is an avatar of Nyx with the intent to bring about the Fall, or end of the world, and end all life on the planet. It is fought on the top of Tartarus during the ninth Full Moon Operation on January 31.

Nyx Avatar is the final boss of Persona 3, fought by SEES. Before becoming the Avatar it was known as Death (or "Thanatos, the bringer of death"), The Appriser, and the harbinger of the Fall. Death is the incarnation of the Arcana that was never meant to be, and because it went through so many changes, Nyx can be recognized as any one of the following entities: Death (Thanatos), Ryoji Mochizuki, Pharos, and Nyx Avatar.

It is a slender and intimidating figure that wears a black, cape like armor by the waist, which has a pair of extremely long tips protruding from it from both sides. It is extremely tall and is likely taller than Arcana Priestess standing up. Its legs are very slender and point tipped, and it also has 4 large wings that are on the same level as its hips. It wears a crown that has a very narrow base and resembles a bowl with 4 broad tips protruding from it. Its sword is abnormally long and is around the same height as the Nyx Avatar itself. Its hairdo is similar to Ryoji's, although its face is now a white mask, and the eyes and mouth of the mask are of a hollow black and presents itself with a blank, frightening smile.

In battle, it harnesses a total of 14 Arcana - from the Fool to its true Arcana, Death. It shifts its Arcana using its unique skill, Arcana Shift, changing its elemental affinities and attacks. During the final phase, it uses two unique skills - Moonless Gown and Night Queen. Moonless Gown reflects all attacks, including Almighty skills. Night Queen deals heavy damage to all opponents, inflicting a myriad of random status effects on the party.

Like the Shadow Arcana, Nyx Avatar represents the inverse interpretation of the Death Arcana. While the Death Arcana represents transition, regeneration, deep change, and cycles, the inverse Death Arcana represents doom, destruction, and an end to everything.

Nyx Avatar is usually regarded as a long boss battle; depending on the player and their progress, it may take an hour.

Nyx Avatar can attack twice each turn (more if its attacks exploit a weakness or strike for critical). The fight consists of 14 different phases, based on its Arcana. Each Arcana has 1,500 HP each, except for the final Death Arcana which has 6,000 HP. In total, the boss has 25,500 HP. Arcana Shift is used in between each phase (regardless of turn order), after its current HP pool has been depleted. Striking Nyx Avatar with a critical hit will confer no benefit aside from additional damage, removing the possibility of All-Out Attacks.

During the final phase, Nyx Avatar will cast Moonless Gown, which lasts for three turn cycles; the turn in which it was cast, the following turn, and will drop it after that. During this time, the boss tends to buff itself, giving the party a chance to safely heal, buff, or debuff, as well (to do this in the non-Portable versions of the game, temporarily change tactics to Heal/Support and then change back once Moonless Gown is over). Don't bother with attacking Nyx Avatar during Moonless Gown as it is impervious to attacks. The third turn of Moonless Gown is also a good opportunity to use Mind or Power Charge.

Night Queen has a chance to Charm party members, which may lead to them casting a full-heal spell on the boss. As such, it is recommended to defeat its final form as quickly as possible. Equipping a Narcissus Flower accessory will resist Charm, and ailment-eliminating items are useful to cure afflicted party members. Using the Infinity fusion spell (Vishnu and Ananta) during this phase will not defend against Night Queen, as it goes through the invulnerability.

As with every boss in the game, Light and Dark attacks are blocked.

Since this is the final boss of the game, players can go liberal with all of the items they have.

During this stage, Nyx will not choose to attack, instead simply "smiling arrogantly" until this stage's HP is depleted. Because of this, it is largely recommended that the player ONLY use Rush to conserve SP/HP and save time.

This stage tends to use its 2 turns to cast Power Charge, followed by any of its strong physical attacks. Immunity to physical attacks protect it against Tetrakarn/Attack Mirrors. Using a Slash/Strike resistant Persona is a good defense against its Almighty Attack. This form takes 50% more damage from Fire, Ice, Electricity, and Wind skills.

This Arcana is defensive-oriented, using Tetrakarn and Makarakarn to reflect attacks and casting status ailments that are boosted via Foul Breath. It attacks using powerful Darkness magic and Almighty Attack.

This is the Nyx Avatar's true and final form, with four times as much HP as the previous phases. It automatically halves the damage of all skills, apart from Almighty - this is distinct from a standard resistance, and therefore cannot be reduced by a Break spell.

Offensively, this phase uses a variety of attacks, including all of the "-dyne" spells, status buffs/debuffs (including Dekaja and Dekunda), Power Charge and Mind Charge, mass status ailment spells, all four elemental break spells, and the usual Almighty Attack.

At about half health, Nyx Avatar will start using Moonless Gown, which reflects all attacks (including Almighty) for three turns. At 2000 HP, it begins to cast spells according to party members' weaknesses, using the elemental "Break" spells to negate their resistances for more damage from its "Ma-dyne" spells. When its HP drops to critical levels (about 1500), it will begin casting Night Queen, which deals heavy Almighty damage to the party and inflicts a random ailment on each member.

"That was my name for a time... I didn't mind it." (responding to Yukari referring to him as Ryoji)

"I am merely a harbinger of the Fall... Though it would be more correct to say that is what I once was."

"There is no longer a distinction to be made between Nyx and myself..."

"What people fear most... What they try to ignore... That is what I am."

"Will you still face me? There must be trembling in your hearts..."

"The moment man devoured the fruit of knowledge, he sealed his fate... Entrusting his future to the cards, man clings to a dim hope. Yes, the Arcana is the means by which all is revealed..." (after defeating Nyx with the Fool Arcana)

"The Arcana is the means by which all is revealed..." (before switching Arcana)

"The moment man devoured the fruit of knowledge, he sealed his fate... Entrusting his future to the cards, man clings to a dim hope. Yet, the Arcana is the means by which all is revealed... Beyond the beaten path lies the absolute end. It matters not who you are... Death awaits you." (switching to Death Arcana)

"You cannot avoid death. To live is to die; they are one in the same..." (before first Moonless Gown activation)

"Let us finish this. It is the path of your choosing." (before first Night Queen Activation)

"Eternity awaits." (casting Arcana Shift)

"It's useless..." (casting Moonless Gown)

"The time has come!" (casting a spell)

"All shall perish." (casting a spell)

"Such a pity... You understand fate, yet you still fight against it with all of your will... If more people were like you, then perhaps the Fall could have been prevented... but it's too late now." (after defeat)

Nyx's presence is so strong that Fuuka Yamagishi is able to sense it without her Persona.

Though using Ryoji Mochizuki as its Avatar, SEES still refers to Nyx and its Avatar as "She" in both "The Journey" and "The Answer".

The Persona 3 Club Book explains that Plumes of Dusk are fragments of Nyx's body that were shed when Nyx's body fused with the moon. They exist in a state between matter and information, having properties of both, and carry within them the same space-time manipulation ability as Shadows - they are essentially physical Shadows.